Telephone diaphragm



July 19, 1927. 1,636,410

L. T. FREDERICK TELEPHONE DIAPHRAGM Filed Aprii 24, 1924 t... July '19, 1927.

UNITED STATES PATENT omen more '1'. rnnnmcx, or vammaarso, mnmna, assrenon r'o rmaoc ntsmrroit column, or vanranarso, nmmn'a, A CORPORATION or nmma.

TELEPHONE DIAPHRAGM.

- Application filed April 24, 1924. Serial No. 708,868.

" I 'My invention relates to telephones, especially of that type in which the diaphragm in the receiver or transmitter is of electromagnetic material, and is consequently re-' sponsive to the fluctuations in the magnetic field in which it is placed. The object of the invention-yis to render the diaphragm more sensitive than the types heretofore known. In order to avoid the effect of hysteresis. it is common to employ soft steel or similar metal approximately .010 inch thick, varnished for appearance and for protection against rust. According to my invention I emplo a composite diaphragm composed of a muc thinner sheet of metal reinforced by means of a lighter material, for example,

synthetic resin condensate.

I accomplish my object by the manner illustrated in the accompanymg drawings, in

which-- Flgurel is an axial sectional V16W of a telephone receiver in which a diaphragm em-- bodying my invention is mounted.

Figure 2 is across section of a diaphragm embodying m invention showing the same in lenticular cm.

Figure 3 is a cross section of adiaphragm of umform thickness.

Figure 4 is a bottom plan view of the magnet shown in Fi re 1 and Figure 5 is a ace view of a. diaphragm embodying my inventioma portion of the outer surface being broken away to show internal construction.

Like numerals denote out the several views.

While the form of mounting for the diaphragm may be greatly varied I have shown a mounting consistin of a casing 1 and a screw 'cap 2 between w oh the diaphra m is clamped when the parts are assem led. Mounted within the are means for producing a fluctuating magnetic-field. As these are known it will be suflicient for the present purpose to say that in the illustrated construction electro-magnetic windings 4, 4 are employed to magnetize cores 5, 5 which are placed in juxtaposition tothe diaphragm in accordance with common practice. Now referring to the diaphragm which constitutes the essence of the invention, I

35 like parts throughprovide a thin disc-6 of soft iron or other suitable metal, the same. having a. number of holes 7 punched therein at various points throughout its extent. This disc instead of being of ordinary thickness is muchthinner, for example .002 or .003 inch, although I do not wlsh to be understood as confining myself to discs as thin as this. This metal disc is embodied in plastic material 8 of a character lighter and more resilient than the metal disc. For this purpose I prefer to use' a synthetic resin condensate. Such condensates are commonly produced chiefly from phenol and formaldehyde and such material is sometimes known as bakelite. This condensate is at first plastic and I produce the composite dlaphragm by molding .the thin disc within the condensate. The molding action is accomplished usually under heat and pressure and during the molding process the condensate will fill the apertures in the metal disc and thus produce a diaphragm which is a unitary structure, but is provided with a magnetic core.

While I prefer the lenticular form shown in Figure 2that is, a diaphragm having the form of a thin double convex lens, it is possible also to employ the fiat form shown in Figure 3. In this case the condensate 9 will be of uniform thickness.

, As the condensate is resilient and much .lighter than metal my composite diaphragm rates much more readily than one made entirely of metal and hence it is muchmore sensitive.

While I have shown the metal core as extending to the periphery of the disc, it may be of smaller diameter. For example it may be confined to the central portion, near the magnetic ole pieces 5, where the-lines of magnetic orce are most concentrated.

It will be understood that the term telephone as herein employed is intended to include loud speakers and other instruments operating upon the electromagnetic principles above described.

I do not herein claim the idea of a lenticular diaphragm broadly, for it forms the sub- I claim as new and desire to secure by Letdisc having a central core of thin sheet metal 1 ters Patent is: embodied in a resilient body of hardened 1. In a telephone, a composite diaphragm plastic material of lenticular form whereby composed of a thin sheet of metal and a the diaphragm as a Whole is thinner at the '5 layer of synthetic resin condensate rigidly periphery than at the central portion.

secured thereto for reinforcing it, and elec- In Witness whereof, have hereunto sub- 15 tromagnetlc means operable on sald sheet for scribed my name. vibrating 1t.

2. In a telephone, a composite diaphragm LOUIS T. FREDERICK. 

